(a) The number of photons

The number of photons is given by:

$\overline{){\mathbf{n}}{\mathbf{=}}\frac{{\mathbf{E}}_{\mathbf{p}\mathbf{u}\mathbf{l}\mathbf{s}\mathbf{e}}}{{\mathbf{E}}_{\mathbf{p}\mathbf{h}\mathbf{o}\mathbf{t}\mathbf{o}\mathbf{n}}}}$

$\overline{)\begin{array}{rcl}{\mathbf{E}}_{\mathbf{photon}}& {\mathbf{=}}& {\mathbf{hv}}\\ & {\mathbf{=}}& \mathbf{h}\frac{\mathbf{c}}{\mathbf{\lambda}}\end{array}}$

A 193nm-wavelength UV laser for eye surgery emits a 0.500mJ pulse. (a) How many photons does the light pulse contain?